Thermochemical water decomposition

High temperature (often exceeding 1000 K) drives the endothermic chemical reactions. Multistep cycles for water splitting are used because very high temperatures are required before an appreciable amount of water decomposes in single-step cycles. Thus, in one or more subsequent chemical reactions, the intermediary compounds can be recovered to the original substance, which is used repeatedly. The thermochemical water decomposition steps involve the following five principal reactions ... 

Alternative methods of hydrogen production are thermochemical water decomposition, photoconversions, photobiological processes, production from biomass, and various industrial processes where it is a by-product. 

YOSHIDA, K., Hydrogen Production by UT-3 Thermochemical Water Decomposition Cycle, Hydrogen and Clean Energy (Int. Symp., Tokyo, 1995), NEDO (1995) 39-46. 

Rosen, M. A. (2008). Exergy analysis of hydrogen production by thermochemical water decomposition using the Ispra Mark-10 Cycle. International Journal of Hydrogen Energy, 33, 6921-6933. 

A simplified schematic of a Cu—Cl cycle for thermochemical water decomposition, showing overall inputs and outputs, operation temperatures, and intermediate steps, is shown in Fig. 19.2. 

Roth, M., K.F. Knoche (1989), Thermochemical Water Splitting Through Direct HI Decomposition from H20-HI-I2 Solutions , Int.J. Hydrogen Energy, 14 (8), 545-549. 

Hwang, G.J. and Onuki, K., Simulation study ou the catalytic decomposition of hydrogen iodide in a membrane reactor with a silica membrane for the thermochemical water splitting IS process. Journal of Membrane Science, 194, 207, 2001. 

Ginosar, D.M., Glenn, A.W., and Petkovic, L.M., Stability of Sulfuric Acid Decomposition Catalysts for Thermochemical Water Splitting Cycles, paper presented at the AlChE Spring Meeting 2005, Atlanta, 2005. 

Decomposition of sulfuric acid presents an efficient means of generating oxygen via a solar thermochemical water splitting cycle pending the required reaction temperatures can be realizable. 

Because these temperatures are impractical, the thermochemical water-splitting cycles achieve the same result (i.e., separation of water into hydrogen and oxygen) at lower temperatures. A thermochemical water-splitting cycle is a series of chemical reactions tliat sum to the decomposition of water. To be useful, each reaction must be spontaneous and clean. Chemicals are chosen to create a closed loop where water can be fed to the process, oxygen and hydrogen gas are collected, and all other reactants are regenerated and recycled [2]. 

M. Roth and K.F. Knoche, Thermochemical water splitting through direct HI decomposition from H2O-HI 12 solutions , Int. J. Hydrogen Energy 14 545-9 (1989). 

In this study, the silica membranes to apply for HI decomposition reaction was investigated, and prepared by the sol-gel and the thermal chemical vapor deposition (CVD) methods. The objective of this work is to study the characteristics of the silica membrane preparation and the hydrogen permselectivity of the membrane reactor used for HI decomposition in the thermochemical water splitting IS process. 

Similar to thermochemical water splitting cycles, hydrogen sulfide decomposition can also be achieved via thermochemical cycles. Some metal- or metal oxide-based cycles are listed as follows ... 

Electrolysis, and thermochemical and photochemical decomposition of water followed by purification through diffusion methods are expensive processes to produce hydrogen. 

Westinghouse A proposed thermochemical process for decomposing water to oxygen and hydrogen by electrolysis, coupled with the high-temperature decomposition of sulfuric acid ... 

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